The present invention relates to a voltage regulating device, and, more specifically to a loop-type voltage regulating device, particularly for regulating a voltage of an automotive electric system, including at least one thermal engine, a voltage regulator and an alternator operative to deliver a system regulated voltage signal to and receive a regulation signal from the voltage regulator, and to a method of loop regulating a voltage.
Automotive electric systems are known to incorporate provisions for regulating the system voltage according to the thermal engine rotational speed.
At low rpm (revolutions per minute), a thermal engine as used for automobile vehicles is bound to develop a low drive torque. In this condition, connecting in an electric load of substantial magnitude, such as an air-conditioning apparatus, may cause the engine to quit because the alternator coupled thereto, in order to supply the amount of current required, would demand a higher torque than the engine can produce.
Shown generally and schematically at 1 in FIG. 1 is a conventional voltage regulating device for an automotive electric system.
The regulating device 1 includes essentially an alternator 2, a battery 3 and a voltage regulator 4, being connected in parallel together.
The voltage regulator 4 includes:
A first terminal TRxe2x80x21, being connected to a first terminal TAxe2x80x21 of the alternator 2 and receiving a phase signal PH;
a second terminal TRxe2x80x22 connected to a second terminal TAxe2x80x22 of the alternator 2 and connected to a voltage reference, specifically a ground voltage GND;
a third terminal TRxe2x80x23 connected to a third terminal TAxe2x80x23 of the alternator 2 and receiving a regulated-voltage signal A+; and
a fourth terminal TRxe2x80x24 connected to a fourth terminal TAxe2x80x24 of the alternator 2 and delivering a regulation signal DF.
Based on the phase signal PH from the alternator 2, the voltage regulator 4 will essentially monitor the regulated-voltage signal A+ and regulate it by means of the regulation signal (or field driver) DF.
Thus, in the regulating device 1, the phase signal PH is utilized to provide an indication of the engine state of operation through the operation of the alternator 2. In fact, with the engine crankshaft coupled to the alternator shaft by a pulley drive, the alternator rpm will be proportional to the engine rpm.
This scheme is found in many commercially available regulators, whereby the phase signal from the alternator is analyzed and different strategies are used, according to the signal width and frequency, to control the system regulated-voltage signal.
FIG. 2 shows in greater detail a voltage regulator 4 of a type currently employed in automotive electric systems.
The voltage regulator 4 comprises a threshold comparator 5 connected between first and second terminals, TRxe2x80x21 and TRxe2x80x22, of the voltage regulator 4, and is biased at its input by a voltage source VB. The threshold comparator 5 is connected with its output to a plurality of switches SW1, . . . SWN which are controlled by a plurality of buffers I1, . . . IN according to the frequency value fPH of the phase signal PH at the first terminal TRxe2x80x21, as well as according to reference values f1, . . . fN set by said buffers I1, . . . IN.
The controlled switches SW1, . . . SWN are connected directly to the fourth terminal TRxe2x80x24 of the voltage regulator 4 as well as to the third terminal TRxe2x80x23 through a plurality of ramp comparators CR1, . . . CRN.
The voltage regulator 4 of FIG. 2 operates as follows. According to the frequency fPH of the phase signal PH at the first terminal TRxe2x80x21, the voltage regulator 4 will regulate the system voltage A+ using different time constants that have been set by the buffers I1, . . . IN according to the operational state of the vehicle engine. In particular, the buffers I1, . . . IN will close one of the switches SW1, . . . SWN to connect, via a ramp comparator CR1, . . . CRN, the third terminal TRxe2x80x23 of the voltage regulator 4, whereat the regulated-voltage signal A+ is present, to the fourth terminal TRxe2x80x24 of the voltage regulator, whereat the regulation signal DF is present.
When no signal is received by the alternator 2, or if its frequency is less than a first reference value f1, no switches SW1, . . . SWN would be closed and the voltage regulator 4 would be switched off to a stand-by condition.
In the presence of a heavy electric load while the engine is at low rpm, the voltage regulator 4 will control the torque to the alternator 2 to increase proportionally, so that a current can be generated to match the load. Thus, an E.C.U. (Engine Control Unit) 6 of an automotive thermal engine 7 is enabled to increase the engine rpm, without switching off the thermal engine 7, as shown schematically in FIG. 3.
In particular, the voltage regulator 4 controls the alternator 2 by means of the regulation signal DF and according to the information received from the alternator 2 itself through the phase signal PH and the regulated-voltage signal A+.
Similarly, the control unit 6 will receive from the engine 7, via a plurality of sensors, various information INF concerning the engine state, and will act on it by a plurality of signals AT, generally designated as actuators.
While being in many ways advantageous, this prior scheme has a drawback in that the voltage regulator 4 obtains the information about the engine operation from the rotational speed of the alternator 2, thus losing concurrence of this information. In fact, by the time that the engine rpm is derived from the alternator rotation, the engine may have changed its state and the voltage regulation proves less than optimum for the system.
The underlying technical problem of this invention is to provide a voltage regulating device, particularly for automotive electric systems, with such structural and functional features as to optimize the system voltage regulation, thereby overcoming the limitations of known devices.
The resolutive idea proposed by the invention is based on using the system control unit to let a voltage regulator know the operational state of the engine in real time.
The disclosed embodiment of the invention is directed to a voltage regulating system and device in an automotive electric system having at least one thermal engine, a voltage regulator, and an alternator operative to deliver a system-regulated voltage signal 2 and receive a regulation signal from the voltage regulator, and further including a control unit within the regulating loop, the control unit connected between the thermal engine and the voltage regulator and adapted to supply the voltage regulator with a signal corresponding to the operation of the engine for regulating the voltage delivered from the alternator. The disclosed embodiments also relate to a method of loop regulating a voltage, in particular a voltage of an automotive electric system, that includes detecting variables related to the operation of a thermal engine by having a control unit connected to the engine; real-time processing the variables detected by the control unit in order to assess the actual conditions of the thermal engine operation; and regulating a system voltage according to the detected engine operating conditions using a voltage regulator connected in turn to an alternator of the thermal engine.